An image processing apparatus is known which comprises an image forming unit for forming an image on a sheet with a decolorable color material and thermally fixing the image on the sheet and an image decoloring unit for decoloring the image formed with the decolorable color material by heating the sheet. In the image processing apparatus, a sheet subjected to decoloring processing by the image decoloring unit is conveyed to the image forming unit to be formed with an image.
A temperature of the sheet on which the image is decolored through a heating processing is temporarily maintained to be high. If an image is formed on the high-temperature sheet with a decolorable color material and fixed, then because of the heat of the sheet, the decolorable color material will be decolored, which disenables the printing of a normal image.